OWC Knowledge base

RAM Compatibility: Substituting PC-133 for PC-100

PC-133 and PC-100 RAM modules are backwards compatible. Higher speed memory modules always default to the highest CAS latency rating at slower speeds. For example, a PC-133 CL3 (3-2-2) chip will run at either PC-100 or PC-66, CL2 (2-2-2). If you purchase ...

RAM: PC-133 RAM (CL2 vs. CL3)

Legacy SDRAM modules for older Macs utilize a small programming chip called the Serial Presence Detect (SPD). This chip tells the computer what it is, and how it should be used. It has Primary, Secondary, and Tertiary programming for CLx settings. In most...

RAM: Installation Videos

If you need assistance installing your memory (RAM) upgrade kit, OWC offers detailed installation videos for a wide variety of Mac models. Please use the link below to find your specific Mac video. http://eshop.macsales.com/installvideos/ [http://eshop....

RAM: Intel Macs - Pairing RAM Modules

Generally, any iMac, non-Retina MacBook, or non-Retina MacBook Pro, or Mac Mini from the last several years should allow RAM modules of the same spec but different capacities to be installed in any of the RAM slots in the computer. There is no specific or...

RAM: Diagnostic Software Tests

Generally the best software-based RAM test you can use for your Mac is the one built into Apple's AHT (Apple Hardware Test) suite. To learn more about the AHT, go to https://support.apple.com/en-us/HT201257 [https://support.apple.com/en-us/HT201257] ...

RAM: How Much Do I Need?

Unfortunately, there is no one correct answer to this question. It depends on the specific Mac you're using, the operating system on that Mac, and the specific software applications you use. While Apple lists only 2GB as the requirement for some operati...

RAM: ECC Errors

ECC (stands for Error Correcting Code) RAM modules are a special type of module used in servers and workstations, typically in scenarios where there is zero tolerance for data errors. Two common examples include scientific computing and financial systems....

RAM: Mac Pro - Blinking White LED

This article applies to the following products: OWC8566D3MPE4GB, OWC8566D3MPE8GB, OWC8566D3MPE16G If your 2009 or 2010 Mac Pro is displaying a blinking white LED, you may have mismatched RAM modules installed. The 4GB, 8GB, and 16GB modules listed above...

RAM: Compatibility - 32GB Modules for MacPro6,1

Due to processor design and memory architecture, 32GB RAM module utilization occurs at a bus speed of 1066MHz with Apple Mac Pro 2013 E5-16XXv2 4-Core, 6-Core, and 8-Core processor equipped models, while factory 12-Core or after-market E5-26XX equipped mo...

RAM: Troubleshooting Tips

PROBLEM The Mac will not start up / it exhibits a beeping sound after startup with new memory (or RAM) modules installed. SOLUTION If you're having trouble getting your Mac to run normally after installing new RAM, there are several things you can do ...

Mac: 2019 Mac Pro: Â Memory Configurations

Relevant Module Types / Base Modules: * 'R DIMMS' * OWC2933D4MP64G * OWC2933D4MP32GB * OWC2933D4MP16GB * OWC2933D4MP8GB * OWC2666D4MPE32G * OWC2666D4MPE8GB * * 'LR DIMMS' * OWC2933D4LR128G * OWC2933D4LR64GB * OWC2666D4LRE64G ...

RAM (OWC2666DDR4Sxxx): Pairing Modules for 2020 iMacs

Recently we determined that OWC RAM modules that are compatible with the August 2020 iMac (iMac20,1 and iMac 20,2), will report and operate at a lower speed (2133 MHz instead of 2666 MHz) when paired with modules from other manufacturers, including Apple ...